Amide branched aromatic gelling agent enhancers and breakers

ABSTRACT

A downhole fluid comprises a base fluid, for example a hydrocarbon base fluid, a gelling agent, and a gel enhancer. The gelling agent has an aromatic core of one or more aromatic rings, the gelling agent having two or more amide branches distributed about the aromatic core, each of the two or more amide branches having one or more organic groups. An example gelling agent is a pyromellitamide gelling agent. A method of making a downhole fluid, the method comprising: combining a base fluid, a gelling agent, and a gel enhancer. A downhole fluid comprising a base fluid, a gelling agent, a breaker, and a gel enhancer. Downhole fluids with such gels and a breaker are also disclosed.

TECHNICAL FIELD

This document relates to amide branched aromatic gelling agent enhancersand breakers.

BACKGROUND

Benzamide gelling agents have been proposed or used in LCD displays andas amide nucleating agents. Pyromellitamide gelling agents have beenproposed or used in tissue engineering, drug delivery, LCD displays, andcatalysis.

SUMMARY

A downhole fluid is disclosed comprising a base fluid and a gellingagent with an aromatic core of one or more aromatic rings, the gellingagent having two or more amide branches distributed about the aromaticcore, each of the two or more amide branches having one or more organicgroups. A gel enhancer, breaker, or both may be added to such a fluid.

A downhole fluid is disclosed comprising a base fluid and apyromellitamide gelling agent. The pyromellitamide gelling agent mayhave the general formula of:

with R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each being a hydrogen or anorganic group.

A downhole fluid is also disclosed comprising a base fluid, a gellingagent, and a gel enhancer, in which the gelling agent has an aromaticcore of one or more aromatic rings, the gelling agent has two or moreamide branches distributed about the aromatic core, and each of the twoor more amide branches has one or more organic groups.

A method is also disclosed comprising introducing the downhole fluidinto a downhole formation. A method of making a downhole fluid is alsodisclosed, the method comprising: combining the base fluid and gellingagent. A composition for gelling a downhole fluid is also disclosed, thecomposition comprising an amide branched aromatic gelling agent and awetting agent.

A gelling agent is also disclosed for a downhole fluid, the gellingagent having the general formula of:

with R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each being a hydrogen or a C7-24alkyl group.

A method is also disclosed comprising using the downhole fluid as adrilling fluid or as a downhole treatment fluid.

A method is disclosed of making the downhole fluid by combining the basefluid, the gelling agent, and the gel enhancer.

A downhole fluid is also disclosed comprising a base fluid, a gellingagent, and a breaker, in which the gelling agent has an aromatic core ofone or more aromatic rings, the gelling agent has two or more amidebranches distributed about the aromatic core, and each of the two ormore amide branches has one or more organic groups.

A downhole fluid is also disclosed comprising a base fluid, apyromellitamide gelling agent, a breaker, and a gel enhancer.

In various embodiments, there may be included any one or more of thefollowing features: Each of the amide branches is connected to thearomatic core via a carbon-carbon or carbon-nitrogen bond. One or moreof the amide branches are connected to the aromatic core via acarbon-nitrogen bond. Each of the amide branches is connected to thearomatic core via a carbon-nitrogen bond. Three or four amide branchesare present. Each organic group is an alkyl group. Each alkyl group is astraight chain alkyl group. Each alkyl group has 6-24 carbon atoms. Thearomatic core is benzene. Each of the amide branches are connected tothe aromatic core via a carbon-nitrogen bond, and each organic group isan alkyl group with 6-24 carbon atoms. One or more of the amide branchesis connected to the aromatic core via a carbon-carbon bond and one ormore of the amide branches are connected to the aromatic core via acarbon-nitrogen bond. Each alkyl group has 6-12 carbon atoms. Thearomatic core is naphthalene. Each of the amide branches has one organicgroup. The gelling agents exclude pyromellitamide gelling agents. Thegelling agent is a pyromellitamide gelling agent. The pyromellitamidegelling agent has the general formula of:

with R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each being a hydrogen or anorganic group. R₅, R₆, R₇, and R₈ are each hydrogens and one or more ofR₁, R₂, R₃, and R₄ is each an alkyl group. R₁, R₂, R₃, and R₄ are eachalkyl groups. R₁═R₂═R₃═R₄. R₁, R₂, R₃, and R₄ each has at least 6 carbonatoms. Each alkyl group has 6-24 carbon atoms. Each alkyl group has 6-10carbon atoms. Each alkyl group is one or more of straight chain,branched, aromatic, or cyclic. Each alkyl group is straight chain. R₅,R₆, R₇, and R₈ are each hydrogens, and R₁, R₂, R₃, and R₄ are eachstraight chain alkyl groups with 6-10 carbon atoms. R₁, R₂, R₃, and R₄have 6 carbon atoms. The base fluid comprises hydrocarbons. Thehydrocarbons have 3-8 carbon atoms. The hydrocarbons have 3-24 carbonatoms. The hydrocarbons comprise liquefied petroleum gas. The base fluidcomprises one or more of nitrogen or carbon dioxide. A breaker is usedor present. The breaker is a water-activated breaker and the downholefluid comprises a hydrate. The breaker further comprises an ionic salt.The ionic salt further comprises one or more of a bromide, a chloride anorganic salt, and an amine salt. The breaker comprises one or more of analcohol or alkoxide salt. The one or more of an alcohol or alkoxide salthas 2 or more carbon atoms. The alkoxide salt is present and comprisesaluminium isopropoxide. The alkoxide salt is present and the downholefluid comprises a hydrate. The breaker comprises a salt of piperidineand the downhole fluid comprises a hydrate. The breaker furthercomprises a coating. The coating further comprises wax. The gel enhancermay be a cross linker. The gel enhancer comprises an organic molecule,such as a heterocycle, with at least two heteroatoms that are spacedfrom one another and each have one or more lone pairs of electrons. Theheterocycle forms a 6 atom ring with the two non carbon atoms located atthe 1 and 4 positions or on respective functional groups originatingfrom the 1 and 4 positions. The heterocycle comprises piperazine. Thegel enhancer comprises one or more of a metal compound, potassiumtert-butoxide, diethanolamine, L-menthol, lactic acid, mandelic acid,ammonium acetate, paraformaldehyde, hydroquinone, andtetramethylammonium hydroxide. The metal compound is present andcomprises one or more of iron and aluminium. The downhole fluid has asurfactant for dispersing the gel enhancer in the base fluid. The metalcompound comprises iron (III) sulfate. The surfactant forms a complexwith the gel enhancer in the base fluid. The metal compound is solublein pure form in the base fluid. The metal compound comprises a metalalkoxide. The metal alkoxide comprises aluminium isopropoxide. The gelenhancer comprises a salt of an aromatic carboxylic acid. The salt of anaromatic carboxylic acid comprises an ibuprofen salt. The gel enhancercomprises one or more of ammonium chloride, melamine, choline chloride,and hexamethylene diaminochloride. The gelling agent forms ahydrogen-bond network through intermolecular hydrogen bonds between theamide branches of adjacent gelling agent molecules, and in which the gelenhancer cross-links the intermolecular hydrogen bonds or facilitatesthe intermolecular hydrogen bonds. The downhole fluid has a modifierselected to convert the gel enhancer into a breaker. The gel enhancer ispresent below a threshold concentration above which the gel enhancerbecomes a breaker, and in which the modifier comprises an additionalsource of gel enhancer sufficient to raise the concentration of gelenhancer to above the threshold concentration. The gel enhancercomprises piperidine or piperazine. The gel enhancer comprisespiperidine and the modifier comprises benzylamine. The gel enhancercomprises a salt of an aromatic carboxylic acid, and in which themodifier comprises a protonation source or a cation complexing agent.The protonation source comprises acid. The cation complexing agentcomprises citric acid and the salt of an aromatic carboxylic acidcomprises ibuprofen salt. The modifier further comprises a coating. Abreaker and a gel enhancer may be present and distinct from one another.The breaker comprises an aromatic carboxylic acid. The breaker comprisesone or more of ibuprofen and hydrocinnamic acid. The breaker comprisesone or more of diphenylacetic acid, benzoic acid, and phenylacetic acid.A cation complexing agent is present, in which the aromatic carboxylicacid is a salt. The aromatic carboxylic acid comprises an ibuprofen saltand the cation complexing agent comprises citric acid. The gelling agentforms a hydrogen-bond network through intermolecular hydrogen bondsbetween the amide branches of adjacent gelling agent molecules, and inwhich the breaker disrupts the intermolecular hydrogen bonds. Thebreaker is a hydrogen bonding agent that forms a hydrogen bond, with theamide branches of the gelling agent, that is stronger than theintermolecular hydrogen bonds between the amide branches of adjacentgelling agent molecules. The downhole fluid is for use as a drillingfluid. The downhole fluid is for use as a downhole treatment fluid.Introducing the downhole fluid into a downhole formation. Fracturing thedownhole formation. Recovering downhole fluid from the downholeformation, and recycling the recovered downhole fluid. Recycling furthercomprises removing a breaker from the recovered downhole fluid. Thegelling agent is provided with a carrier. The carrier comprises glycol.The gelling agent is provided with a wetting agent. The gelling agent isprovided with a suspending agent. Combining is done on the fly beforeintroducing the downhole fluid into a downhole formation.

These and other aspects of the device and method are set out in theclaims, which are incorporated here by reference.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the figures, inwhich like reference characters denote like elements, by way of example,and in which:

FIG. 1 illustrates hydrogen bond formation.

FIG. 1A shows the basic structure of an amide branched aromatic gellingagent.

FIG. 1B shows on the left and right an amide branch connected to thearomatic core via a carbon-nitrogen bond and a carbon-carbon bond,respectively.

FIG. 2 illustrates a proposed solvation interaction between an alkylsolvent and a pyromellitamide gelling agent with straight chain alkylgroups.

TABLE 1 Characteristics of viscosity testing of disclosed gellingagents. Viscosity testing was carried out a Brookfield viscometer. TB,TH, TO and TD refer to N,N′,N″,N′″-tetrabutylbenzene-1,2,4,5-tetracarboxamide (TB), N,N′,N″,N′″-tetrahexylbenzene- 1,2,4,5-tetracarboxamide (TH), N,N′,N″,N′″-tetraoctylbenzene-l,2,4,5-tetracarboxamide (TO), and N,N′,N″,N′″-tetradecylbenzene-1,2,4,5-tetracarboxamide (TD), respectively. GellingAgent Gelling Concentration Shear Rate Temperature FIG. Agent (mM)Solvent (sec⁻¹) (° C.) 3 TH 10 TG740 100 varying 4 TO 10 TG740 100varying 5 TD 10 TG740 100 varying 6 TB 10 Cyclohexane 100 varying 7 TB 7Cyclohexane 100 varying 8 TB 5 Cyclohexane 100 varying 9 TB 4Cyclohexane 100 varying 10 TB 3 Cyclohexane 100 varying 11 TB 2Cyclohexane 100 varying 12 TB 1 Cyclohexane 100 varying 13 TH 7 TG740100 varying 14 TH 5 TG740 100 varying 15 TH 4 TG740 100 varying 16 TH 3TG740 100 varying 17 TH 2 TG740 100 varying 18 TH 1 TG740 100 varying 19TO 7 TG740 100 varying 20 TO 5 TG740 100 varying 21 TO 4 TG740 100varying 22 TO 3 TG740 100 varying 23 TO 2 TG740 100 varying 24 TO 1TG740 100 varying 25 TD 7 TG740 100 varying 26 TD 5 TG740 100 varying 27TD 4 TG740 100 varying 28 TD 3 TG740 100 varying 29 TD 2 TG740 100varying 30 TD 1 TG740 100 varying 31 TH:TO 2:2 TG740 100 varying 32TH:TO 2:2 TG740 100 varying 33 TO:TD 2:2 TG740 100 varying 34 TO:TD 2:2TG740 100 varying 35 TH:TD 2:2 TG740 100 varying 36 TB 7 Cyclohexane 10025 37 TB 7 Cyclohexane 400 25 38 TB 7 Cyclohexane 500 25 39 TB 7Cyclohexane varying 25

FIG. 40 is a graph of the data from FIG. 39, illustrating viscosity atdifferent shear rates.

FIG. 41 is a graph of shear rate v. shear stress from the data of FIG.39, illustrating non-newtonian behavior.

FIG. 42 is a graph of viscosity v. concentration for TB in cyclohexane.

FIG. 43 is an illustration of various pyromellitamide rotamers.

FIG. 44 is an ¹H NMR spectrum for TH.

FIG. 45 is a ¹³C NMR spectrum for TH.

FIG. 46 is an ¹H NMR spectrum for TO.

FIGS. 47 and 48 are ¹³C NMR spectra for TO. FIG. 48 is an expansion of aportion of the spectrum from FIG. 47 that illustrates the alkyl peaks.

FIG. 49 is an expansion of the ¹H NMR spectrum for TO from FIG. 46.

FIG. 50 is ¹H NMR spectra for TH at varying temperatures of 25, 30, 50,and 70° C. from the bottom spectrum to the top spectrum respectively.

FIG. 51 is ¹H NMR spectra for TO at varying temperatures of 25, 30, 50,and 70° C. from the bottom spectrum to the top spectrum respectively.

FIG. 52 is a graph of the amide hydrogen shift temperature dependencefor TO.

FIG. 53 is a graph of the amide hydrogen shift temperature dependencefor TH.

FIG. 54 is a graph of the viscosities achieved with various amounts ofglycol added to TG740 frac fluid. The glycol solution was made up of0.87 g tetra hexyl pyromellitamide (TH) in 100 mL of glycol with Dynol604 surfactant (15 mM TH concentration).

FIG. 55 is a graph of viscosity v. time of a gelled mixture of 5 mM THin TG740 after addition of tetrabutyl ammonium bromide in pure form andin wax form.

FIG. 56 is a graph of viscosity v. time of a gelled mixture of 5 mM THin SD810 after addition of tetrabutyl ammonium bromide in pure form andin wax form.

FIG. 57 is a graph of viscosity and temperature v. time for 10 mMN,N′,N″-trihexyl, N′″-benzyl benzene-1,2,4,5-tetracarboxamide in SF840.

FIG. 58 is a graph of viscosity v. time for a 15 mM gel of TH in SF840with Dynol 604, after being left overnight and then having variousamounts of iron gel enhancer added.

FIG. 59 is a graph of viscosity v. time for a mixture of SF840 and a 10mL composition of TH (10 mM concentration), Dynol 604, glycol, andthamesol on max blending with various amounts of iron gel enhancer addedto the base fluid.

FIG. 60 is a graph of viscosity v. time for a mixture of SF840 and a 5mL composition of TH (10 mM), Dynol 604, glycol, and thamesol on maxblending with various amounts of iron gel enhancer added.

FIG. 61 is a graph of viscosity v. time for various tetrabutyl ammoniumderivative breakers.

FIG. 62 is side elevation view illustrating a system and method ofmaking a downhole fluid and a method of using a downhole fluid.

FIG. 63 is a side elevation view of a drill bit drilling a well.

FIG. 64 is a graph of the viscosities of various 1,2,4,5 substitutedtetra-amides.

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described herewithout departing from what is covered by the claims.

Referring to FIGS. 1A-B, amide branched aromatic compounds are disclosedin this document as being useful gelling agents for downhole fluids. Agelling agent is an agent that thickens a fluid. Such gelling agentshave an aromatic core of one or more aromatic rings as shown in FIG. 1A.Two or more, for example, three to six or more, amide branches aredistributed about the aromatic core, each of the two or more amidebranches having one or more organic groups. Each of the amide branchesmay be connected to the aromatic core via a carbon-carbon orcarbon-nitrogen bond as shown in FIG. 1B.

One example of an amide branched aromatic gelling agent is apyromellitamide. Pyromellitamides have the general base structure (1)shown below:

Pyromellitamides are disclosed in this document as being useful gellingagents for downhole fluids.

For example, a suitable gelling agent may have the general formula of:

with R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each being a hydrogen or anorganic group. The description below of variations of the organic groupsapplies to the organic groups discussed for all embodiments disclosed inthis document. R₅, R₆, R₇, and R₈ may each be hydrogens (example nonorganic group) and one or more or all of R₁, R₂, R₃, and R₄ may each bean alkyl group (an example of an organic group). In some cases,R₁═R₂═R₃═R₄. R₁, R₂, R₃, and R₄ may each have 6 carbon atoms, forexample, 6-10 or 6-24 carbon atoms. Each alkyl group may be one or moreof straight chain, branched, aromatic, or cyclic. However, preferablyeach alkyl group is straight chain, for example if R₅, R₆, R₇, and R₈are each hydrogens, and R₁, R₂, R₃, and R₄ are each straight chain alkylgroups with 6-10 carbon atoms. In one example, R₁, R₂, R₃, R₄, R₅, R₆,R₇, and R₈ are each hydrogen or a C7-24 alkyl group. The organic groupsmay include functional groups such as esters. In addition to thepyromellitamides synthesized and tested below, example pyromellitamidessynthesized and successfully used to gel TG740 include compounds whereR₅, R₆, R₇, and R₈ are each hydrogens, and R₁═R₂═R₃═R₄, and R₁ equalsn-pentyl (from 1-pentylamine used in amide synthesis), R₁═CH(Me)CH2CH3(from 2-aminobutane used in amide synthesis), R₁═CH(Me)CH2CH2CH2CH2CH3(from 2-aminoheptane used in amide synthesis), R₁═CH(Me)CH2CH2CHMe2(from 2-amino-5-methylhexane used in amide synthesis), andR₁═CH2CH(Et)CH2CH2CH2CH3 (from 2-ethylaminohexane used in amidesynthesis). Also tested were tetracyclohexyl, tetrabenzyl, tetraallyl,tetra n-butyl and tetra t-butyl pyromellitamides.

Downhole fluids, such as downhole treatment fluids, containing suchgelling agents may comprise a base fluid, such as a hydrocarbon basefluid for example with 3-8 carbon atoms, for further example liquefiedpetroleum gas. In other embodiments C3-24 hydrocarbon fluids may beused. In some embodiments, the gelling agent and the downhole fluidcontain no phosphorus. The basic structure of the amide branchedaromatic gelling agents disclosed here is believed to be primarilyresponsible for the gellation mechanism, with variation in the sidechains being useful to tailor the resultant gel. The successful testsand disclosure reported here, as well as the properties and mechanismsreported here, support use of amide branched aromatic andpyromellitamide gels with other non-tested base fluids, for example,non-polar and hydrocarbon based fluids. Utility is soundly predicted forthe disclosed but untested entities, including gels, gel enhancers,breakers, fluids, and other compounds reported here, based on a soundprediction that such entities have the same relevant properties as therespective tested entities.

Downhole fluids may also comprise a suitable breaker, such as an ionicsalt, for example comprising one or more of a bromide a chloride, anorganic salt, and an amine salt, such as a quaternary amine salt. Smallanion cooperativity (1 equivalent) (e.g.chloride>acetate>bromide>nitrate) may induce the gel to solutiontransition by decreasing viscosity by a factor of 2-3 orders ofmagnitude. The time for the gel to collapse may be proportional to thebinding strength of the anion.

The breaker may comprise one or more of an alcohol or alkoxide salt, forexample, with 2 or more carbon atoms, such as propanol. The alkoxidesalt may comprise aluminium isopropoxide. In some cases the breaker mayneed a source of water to activate the breaker to break the gel, forexample if a solid alkoxide like aluminium isopropoxide is used. Thewater source used may be connate water from the formation. In some casesa hydrate or other compound capable of releasing water at a delayed ratemay be used for example by inclusion in the injected downhole fluid. Forexample, the hydrates disclosed in Canadian patent document no. 2685298may be used, and include hydrated breakers having a crystallineframework containing water that is bound within the crystallineframework and releasable into the fracturing fluid. For example,hydrates of any one of magnesium chloride, sodium sulfate, bariumchloride, calcium chloride, magnesium sulphate, zinc sulfate, calciumsulphate, and aluminum sulphate may be used. NaSO4-10H2O may be used asan example of a sodium sulfate hydrate. An ionic salt hydrate orcovalent hydrate could be used. A combination of breaker coating orencapsulation with crystallized water addition may be used.

Another example of a water activatable breaker is a piperidine salt.Unlike piperazine, a breaker with one amine disrupts the hydrogen bondnetwork believed to be responsible for gelling the gels. Piperidine isan effective breaking agent but is a liquid and thus not alwayspractical to use as a breaker on a large scale. Therefore the hydrogenchloride salt of piperidine, piperidine hydrochloride was synthesizedand tested as a solid breaker. There was no major change in viscosityonce the piperidine hydrochloride was added to a 100 mL TH in TG740 gelsolution. Once a small amount of water (20 drops) was added thesolution's viscosity decreased noticeable although the two layers seemedslightly immiscible as there were several bubbles in the solution.

An exemplary procedure for synthesizing a piperidine salt, in this casepiperidine hydrogen chloride is as follows. A round bottom flask wascharged with aqueous hydrochloric acid (2 M, 58.5 mL) before beingcooled to 0° C. using an ice bath. Piperidine (10.0 g, 117 mmol, 11.6mL) was added dropwise over 30 minutes whilst the solution was stirredvigorously. Once all the piperidine had been added the solvent wasremoved and the yellow solid recrystallised from ethanol, filtered andwashed with cold ethanol to give the desired piperidine hydrochloride asa white solid. Yield was 0.95 g, 7.82 mmol, 6.7%, mp: 245 oC, (lit.246-247 oC).

Breakers that were tested and showed a noticeable decrease in viscosityonce added to the gel include: 1-dodecanol>98%, Benzyltriethylammoniumchloride 99%, Tetrabutylammonium hydrogen sulfate 99%, Sodium tosylate95%, Iron (III) sulfate 97%, 2-Chloride-N—N-diethylethylamine hydrogenchloride 99%, Thiodiglycolic acid 98%, Pyruvic acid 98%, 2-hydroxybenzylalcohol 99%, Azelaic acid 98%, Glutaric acid 99%, Malonic acid 99%,1-octylamine 99%, Cyclohexylamine 99%, L-ascorbic acid 99% Acetamide 99%Poly(vinyl) alcohol 89,000-98,000 99%, Ethylenediamine 99.5%,Beta-alanine 99%, L-proline 99%,

Breakers that were tested and showed a slight decrease in viscosity onceadded to the gel include: Benzyltributylamonium chloride>98%, T-butanolanhydrous 99.5%, 2-ethyl-1-butanol 98%, 2-ethyl-1-hexanol 99.6%,1-hexanol 99%, 1-butanol 99.8%, 2-aminobutane 99%, 2-ethyl-1-hexylamine98%, Benzylamine 99%, Piperidine 99%, Propan-2-ol 99.7%,Benzyltrimethylammonium hydroxide 40 wt % in methanol,Tetra-n-butylammonium hydroxide 40 vol % in water.

The breaker may be configured to delay breaking action. For example, atime delay breaker may be achieved by coating the breaker, for examplewith a material selected to release the breaker at a predetermined rateover time downhole, for example wax. Referring to FIGS. 55-56, graphsare provided that illustrate the delay in breaking action when a waxcoating is used on a breaker, in this case tetrabutyl ammonium bromide(pure form, lines 42 and 46, wax, lines 40 and 44). 5 mM solutions of THwere prepared in both TG740 and SD810 and the molar equivalent oftetrabutyl ammonium bromide (0.8 g) or wax-coated tetrabutyl ammoniumbromide (1.0 g) was added to the solutions. The change in viscosity wasmeasured using a chandler viscometer. The results the TH mixture withTG740 showed initial viscosities of 93.6 and 68.3 cPa for waxed andunwaxed breaker, respectively while the SD810 showed initial viscositiesof 97.7 cPa and 100.3 for waxed and unwaxed breaker, respectively. WithTG740 there was a marked difference between the wax coated and purebreaker while with SD810 the difference was muted although delayedaction was observed. The wax breaker action in SD810 had a slower ratein the drop in viscosity compared with the pure breaker. However bothwaxed and unwaxed breaker in SD810 showed a slower rate of degradationcompared to that done with TG740.

Compounds that were visually tested as breakers and showed no decreasein viscosity or in some cases an increase in viscosity once added to thegel include: 1,3-dihydroxyl benzene (resorcinol) 99%, Diphenylaceticacid 99%, Imidazole 99%, Propionamide 97%, Magnesium carbonate, Citricacid 99.5%, Benzoic acid 99.5%, Phenylacetic acid 99%, Potassiumphthalimide 98%, Pentaerythrite 99%, 1-butylamine 99.5%, 1-hexylamine99%, Hydroxylamine hydrogen chloride 98%, Ethanolamine 98%, L-histidine99%, Aspartic acid 98%, Glycine 99%, D-Sorbitol 98%. These and othercompounds may be used as gel enhancers or thickeners in addition to thegelling agent.

Compounds that were visually tested as breakers and showed an increasein viscosity once added to the gel include: Potassium tertbutoxide 95%,Piperazine 99%, Diethanolamine 98%, L-menthol 99%, Lactic acid 85%,Mandelic acid 99%, Ammonium acetate 98%, Paraformaldehyde 95%,Hydroquinone 99%, Tetramethylammonium hydroxide 25 vol % in water. Theseand other compounds may be used as gel enhancers in addition to thegelling agent.

Table 0 below illustrates further testing done on potential breakers.Tests were carried out using 10 mM TH in TG740 (42 cm³) for 30 minuteswith a shear rate of 100 s⁻¹ and standard pressure. The baselineviscosity was calculated as: Maximum viscosity (21° C.)=327.41 cP,minimum viscosity (50° C.)=154.69 cP.

TABLE 0 Viscosity Test Results on potential breakers. Min Conc:viscosity: Breaker name mmols cP Category No breaker (baseline) N/a154.69 N/a Piperidine 80.0 203.92 Enhancer Piperidine 160.0 87.69Breaker Piperidine 240.0 63.08 Breaker Piperidine 320.0 42.40 Breaker1-Butanol 80.0 46.99 Breaker 1-Hexanol 80.0 12.83 Breaker Isopropanol80.0 78.23 Breaker 2-ethyl-1-hexylamine 80.0 16.67 Breaker Ammoniumchloride 80.0 169.31 Enhancer Benzylamine 80.0 103.13 Breaker2-ethyl-1-hexanol 80.0 21.62 Breaker Piperidine plus benzylamine 80.056.18 Breaker 80.0 Choline chloride 80.0 238.63 Enhancer Melamine 80.0226.49 Enhancer Benzyltri-n-butylammonium chloride 80.0 0.51 BreakerSodium hydroxide 80.0 72.55 Breaker Benzyltrimethylammonium hydroxide80.0 3.07 Breaker 40% w/w in MeOH Methanol 80.0 6.14 Breaker Methanol48.0 36.91 Breaker Hexamethylene diaminochloride 80.0 256.90 EnhancerIbuprofen tablets (200 mg) 80.0 19.83 Breaker Tetrabutylammonium bromide80.0 86.36 Breaker Triphenylphosphine 80.0 100.58 Breaker Ammoniumchloride (finely ground) 80.0 158.61 Enhancer Hydrochloric acid 80.090.41 Breaker Sodium hydroxide (finely ground) 80.0 51.13 BreakerToluene 80.0 80.01 Breaker Tetrahydrofuran 80.0 68.82 Breaker1,3,5-trimethylhexahydro-1,3,5- 80.0 91.42 Breaker triazine2-aminoheptane 80.0 7.84 Breaker Water 80.0 147.53 Breaker Ibuprofensodium salt 80.0 166.67 Enhancer Ibuprofen sodium salt plus 80.0 0.54Breaker citric acid 80.0 Citric acid 80.0 109.25 Breaker Pure Ibuprofen80.0 13.48 Breaker Hydrocinnamic acid 80.0 29.31 Breaker Phenylaceticacid 80.0 13.78 Breaker

Referring to FIG. 61, a comparison of various tetrabutyl ammoniumderivative breakers is illustrated. Reference numerals 48, 50, 52, 54,and 56, identify the viscosity v. time curves of TG740 gelled with THand broken with tetrabutyl bisulfide, tetrabutyl nitrate, tetrabutylbromide, tetrabutyl borohydride, and tetrabutyl acetate, respectively.Tetrabutyl bisulfide showed no breaker activity, while at least tetrabutyl nitrate showed delayed breaker characteristics. The latter threetetrabutyl derivatives showed fast breaker action. In some embodimentsnon halogenated breakers may be used as a less toxic alternative tohalogenated breakers.

As discussed elsewhere in this document the gelling agent may form ahydrogen-bond network through intermolecular hydrogen bonds between theamide branches of adjacent gelling agent molecules, and the breaker maydisrupt the intermolecular hydrogen bonds. Suitable breakers may includehydrogen bonding agents that form a hydrogen bond, with the amidebranches of the gelling agent, that is stronger than the intermolecularhydrogen bonds between the amide branches of adjacent gelling agentmolecules. Aromatic carboxylic acid breakers are believed to operate insuch a fashion. The protonated COOH moiety is expected to have improvedsolubility in the hydrocarbon phase relative to the deprotonated COO—version discussed below as a gel enhancer. The strength of the hydrogenbond formed by the COOH moiety results in the COOH moiety preferentiallyhydrogen bonding to the gels and to other COOH molecules, thusdisrupting the gel network at concentrations past a thresholdconcentration. If a cation complexing agent such as citric acid is usedin conjunction with an aromatic carboxylic acid salt, the COO— moietyhas improved solubility in the hydrocarbon phase and may lead to abreaking effect as well, for example, see Table 0 regarding the exampleof ibuprofen salt with citric acid.

Some breakers may also function as gel enhancers, as further discussedbelow.

The downhole fluids disclosed herein may incorporate other suitablechemicals or agents such as proppant. The downhole treatment fluidsdisclosed herein may be used in a method, for example a fracturingtreatment as shown in FIG. 62, of treating a downhole formation. Thegelling agents may be used in oil recovery enhancement techniques.

Referring to FIG. 62, a method and system is illustrated, althoughconnections and other related equipment may be omitted for simplicity ofillustration. A base fluid, such as a hydrocarbon frac fluid, is locatedin storage tank 10 and may be passed through piping 12 into a well 22and introduced into a downhole formation 24, such as an oil or gasformation. Gel may be combined with the base fluid to make a downholefluid. For example, gel may be added on the fly from a gel tank 14, ormay be pre-mixed, for further example in tank 10. Other methods ofgelling the base fluid may be used. For example, batch mixing may beused to make the gel. Other storage tanks 16 and 18 may be used asdesired to add other components, such as proppant or breaker,respectively to the downhole fluid.

The gelling agent may be provided with a carrier, for example an inertcarrier like glycol (ethylene glycol). Referring to FIG. 54, a graph ofthe viscosities achieved by mixing into TG 740 varying amounts of asolution of glycol with 15 mM TH is shown. The gel was initially formedafter 30 seconds of blending in TG-740 frac fluid. As the concentrationof glycol increased, the viscosity of the final mixture increased. Gelformation was almost immediate. Glycol is considered suitable becausethe gelling agent won't gel the glycol. Instead, the carrier provides amedium for dispersing the gelling agent as a dissolved liquid orsuspended solid prior to being combined with base fluid. The gellingagent may be ground prior to mixing with carrier if the gelling agent issolid, in order to facilitate dispersion or dissolution. Once mixed withbase fluid, the carrier dissolves in the base fluid, for examplehydrocarbon base fluid, facilitating dissolution of the gelling agent inthe base fluid without interfering with gelling. Using a carrier allowsthe gelling agent to be stored or transported in a low viscosity statewithin the carrier whilst facilitating quicker dissolution into andhence quicker gelling within the base fluid than could be accomplishedwith solid or neat gelling agent. Other carriers may be used includingacetonitrile or glycerine, for example thamesol.

To facilitate dispersion in the carrier the gelling agent may beprovided with a suspending agent such as clay. The suspending agent mayact as a thickener to suspend the gel in the carrier. The suspendingagent helps to maintain the gelling agent in homogeneous dispersionwithin the carrier, and slows or stops the gelling agent from settlingwithin the carrier. Other suspending agents may be used, such as variouspolymers.

The gelling agent may be provided with a wetting agent, such as asurfactant. For example, in the mixture tested in FIG. 54, DYNOL™ 604surfactant by Air Products™ is used as the surfactant. DF-46 is theglycol/DYNOL™ 604/pyromelitamide mixture. The wetting agent may be usedto help wet the surface of the solid amide branched aromatic andpyromellitamide gels, thus speeding up the dissolution of the solid andimproving time to gel. For example, time to achieve viscosity may beunder four minutes and further under a minute or 30 seconds for amixture of hydrocarbon base fluid and a solution of pyromellitamidegelling agent, glycol, suspending agent, and DYNOL™ 604 surfactant.Other wetting agents may be used, such as DYNOL™ 607.

Referring to FIG. 62 the downhole fluid may be recovered from thedownhole formation 24, for example, through a recovery line 28, andrecycled, for example using one or more recycling apparatuses 26. Therecycling stage may incorporate removal of one or more compounds withinthe recovered fluid, for example if breaker is removed. Distillation maybe used, for example, to remove alcohol or amine, and aqueous separationmay be used, for example, to remove salts.

When the R groups contain non alkyl functionality, for example as shownbelow in structure (3) with ester functionality, aggregation may beinhibited in hydrocarbon fluid compared to when the R groups are alkyl.This effect may be attributed to the fact that the ester group increasespolarity of the compound, thus decreasing solubility in hydrocarbonfluids, and the ester group reduces geometric compatibility with thealkyl containing hydrocarbon fluids used.

Exemplary Synthesis and Related Testing

The synthesis of tetra alkyl pyromellitamides may be carried out in twostages, although other routes and stages may be used:

1. benzene-1,2,4,5-tetracarbonyl tetrachloride (4) synthesis:

2. amide synthesis:

An exemplary procedure for route 1 is as follows. Phosphoruspentachloride (45 g, 0.22 mol) and pyromellitic anhydride (25 g, 0.11mol) were placed in a round bottom flask and mixed together. A hairdryer was used to heat one spot of the flask to initiate the reaction,causing liquid POCl3 to be produced. Once the reaction had beeninitiated an oil bath was used to heat the flask to continue thereaction. Once all the solid had melted the POCl3 by-product wasdistilled off (80-95° C.), and the product was then reduced under vacuum(150-180° C.) using a Kugelrohr machine, yielding the desired product asa white solid (23.7838 g, 73.0 mmol, 66.4%).

An exemplary procedure for route 2 is as follows, albeit without usingpyridine. Benzene-1,2,4,5-tetracarbonyl tetrachloride (2.0 g, 6.0 mmol)in dry tetrahydrofuran (15 mL, 185.0 mmol) was added dropwise to asolution of triethylamine (3.5 mL, 25.0 mmol), hexylamine (3.23 g, 31.2mmol) in dichloromethane (15 mL, 235.0 mmol) and dry tetrahydrofuran (15mL, 185.0 mmol) whilst the solution was stirred vigorously. Afteraddition was complete the reaction was allowed to stir overnight at roomtemperature, before the product was filtered off and the solvent removedusing a rotary evaporator. The crude product was subsequently washedwith methanol and acetone to give the desired pure product as a whitesolid. Yields achieved ranged from 0.20 g, 0.34 mmol, 5.7%, to 0.49 g,0.82 mmol, 13.7%, to 1.26 g, 2.11 mmol, 35.2%. In the example procedurethat led to the 35.2% yield, the hexylamine and triethylamine solutionwas cooled to 0° C. before the acid chloride was added. The reaction wasalso kept at this low temperature throughout the addition of the acidchloride and for an hour after addition had been completed. Thisalteration in conditions led to less precipitate being formed, which wasbelieved to be the unwanted triethylammonium chloride salt and any imidethat had formed, thus showing that low temperatures help form thecorrect product rather than the unwanted imide, as reflected in theimproved yield obtained (35.2%).

Gel Test. To test the samples prepared, a sample of the compound to betested was placed in a glass vial with a few mL of solvent, and thesample was heated until a clear solution formed or until the boilingpoint of the solvent was reached. After cooling if viscosity could bedetected the compound was said to gel the solvent.

Gelation mechanism. Referring to FIG. 1, it has been proposed that amidebranched aromatic and pyromellitamide gelation is achieved through π-πinteractions and primarily intermolecular hydrogen bonds between amidegroups, according to the structural interaction shown.

Table 2 below indicates the results of gel testing of four compounds,TB, TH, TO, and TD. TB, TH, TO and TD refer to structure (1) above eachwith four butyl, hexyl, octyl, or decyl, alkyl groups to giveN,N′,N″,N′″-tetrabutylbenzene-1,2,4,5-tetracarboxamide (TB),N,N′,N″,N′″-tetrahexylbenzene-1,2,4,5-tetracarboxamide (TH),N,N′,N″,N′″-tetraoctylbenzene-1,2,4,5-tetracarboxamide (TO), andN,N′,N″,N′″-tetradecylbenzene-1,2,4,5-tetracarboxamide (TD),respectively. In Tables 2 and 3, TG indicates the formation of atransparent gel, TG* indicates formation of a transparent gel only withheating, I indicates insoluble, S indicates soluble, P indicates thatthe compound gels but precipitates on subsequent cooling, PG indicatespartial gelling with liquid solvent only after shaking, with thesolubility of the molecule requiring heating to get it to dissolve inthe liquid, and X equals no gel formed as the compound is not soluble inthe liquid.

TABLE 2 Gelling properties of various solvents solvent Ethyl DiethylToluene Methanol Acetone Water ethanoate ether Pentane Hexanecyclohexane TB TG P P I I I I I TG* TH TG P P I I TG TG TG TG TO TG I II I TG TG TG TG TD TG I I I I TG TG TG TG

Table 2 indicates that TB, TH, TO, and TD gel non-polar, aproticsolvents. This result is consistent with the fact that intermolecularH-bonding is responsible for the gel structure.

TABLE 3 Gelling properties in SYNOIL ™ products TG740 - BP SF800 - BPSF840 -BP range: range: range: Compound 70-170° C. 125-270° C. 150-330°C. TB X X X TH TG PG PG TO TG PG PG TD TG PG PG Decreasing solubility −>

Table 3 indicates that without agitation not all solvent may beaggregated into the gel. With shaking TG740 obtains uniform viscosity.SF800 and SF840 were never completely incorporated.

Referring to FIG. 2 and Table 4 below, an explanation of the gel testingresults in Tables 2 and 3 may be that alkyl compound chains line upbetter with alkyl solvent chains than with aromatic solvent chains,which are more polar than straight chain alkyls. In addition, stericsmay play a role.

TABLE 4 SynOil Hydrocarbon Product Aromatic content TG740 10% DecreasingSF800 20% Gelation SF840 35% ↓

The gelling agent may be provided with increased aromatic character inorder to improve solvation with aromatic solvents. Referring to FIG. 57for example, a gelling agent was tested and made with R₁, R₂, and R₃being hexyl alkyl groups, R₅, R₆, R₇, and R₈ being hydrogens, and R₄being a benzyl group to add aromatic character and improve aromaticviscosity. The sample tested in FIG. 57 had a 10 mM concentration inSF840, and illustrated gelling action.

Solvation temperature testing.

Referring to FIGS. 3-5 and Table 5 below, viscosity test results for TH,TO, and TD in TG740 at 10 mM concentration are illustrated. The resultsillustrate that increased chain length=increased solubility as thecompound becomes less polar, and decreased viscosity due to reducedH-bond strength. Increased viscosity was almost instant obtained at roomtemperature. An additional but successful experiment not in the figuresor tables involved injecting highly concentrated gelled sample TH inTG740 into ungelled TG740 in a blender at room temperature.

TABLE 5 Min. Time Temp. Gel type Max viscosity (cp) (mins) (° C.) to GelTH 707 85 40 TO 421 50 29 TD 256 40 26

As indicated above, TB did not gel TG740. TB was found to be insolublein TG740, although soluble in cyclohexane. When cyclohexane gelled withTB was injected into TG740, a cloudy dispersion resulted and TG740 wasnot gelled.

FIGS. 3-30 illustrate viscosity testing results for TB, TH, TO and D asindicated in Table 1 above. Many of the results, for example the resultsshown in FIGS. 13-15 for TH gelled TG 740, indicate that increasingtemperature increased viscosity, which was unexpected.

Referring to FIGS. 31-35 and Table 6, various mixtures of gelling agentswere tested. Such mixtures demonstrated thermoreversible gelling, whichis in line with the theory that reversible H bonding between moleculeswas responsible for gelling. The mixture results also demonstrate thatgelling is temperature dependent and chain length dependent.

TABLE 6 THTO THTD TOTD Max viscosity (cp) 21 15 12 Min viscosity (cp) 136 5

Tables 7-10 below illustrate viscosity testing results for TB, TH, TO,and TD, respectively.

TABLE 7 Viscosity test results for TB in cyclohexane Max. Temp. max Min.Temp. min viscosity viscosity reached viscosity viscosity Conc. (mM)(cP) (° C.) (cp) reached (° C.) 10 436 42 303 25 7 119 25 35 48 5 85 2439 47 4 56 24 16 49 3 25 25 3 48 2 20 25 14 48 1 9 25 4 47

TABLE 8 Viscosity test results for TH in TG740 Temp. max Min. Temp.Conc. Max. viscosity reached viscosity min viscosity (mM) viscosity (cP)(° C.) (cp) reached (° C.) 7 301 22 198 27 5 130 48 107 25 4 79 40 69 243 45 31 40 48 2 19 25 9 48 1 7 24 0 28

TABLE 9 Viscosity test results for TO in TG740 Temp. max Temp. min Conc.Max. viscosity viscosity Min. viscosity viscosity (mM) (cP) reached (°C.) (cp) reached (° C.) 7 219 35 196 26 5 116 38 110 48 4 83 33 74 48 343 24 33 48 2 19 25 10 48 1 7 25 3 48

TABLE 10 Viscosity test results for TD in TG740 Max. Temp. max Temp. minConc. viscosity viscosity reached Min. viscosity reached (mM) (cP) (°C.) viscosity (cp) (° C.) 7 124 26 71 48 5 64 25 33 48 4 43 25 19 48 326 25 14 48 2 8 23 0 47 1 2 24 0 47

FIGS. 36-41 illustrate shear testing results for TB in cyclohexane. Theresults shown in FIGS. 36-39 illustrate that the gels formed may beshear stable, as illustrated by testing with a constant shear rate overtime. FIGS. 39-41 examine the viscosity of TB in cyclohexane under avarying shear rate, and illustrate that there is a nonlinearrelationship between shear rate and shear stress, thus indicatingNon-Newtonian behavior.

Referring to FIG. 42, an examination of TB gelation in cyclohexane atdifferent concentrations illustrated a non-linear relationship betweenviscosity and concentration as shown. This finding supports the theorythat the formation of gels is thought to occur via a hierarchicalself-assembly of columnar stacks, helical ribbons and similar aggregatesto form a 3D network.

Nuclear Magnetic Resonance Spectroscopy (NMR)

NMR was used to determine molecular structure, and is based on radiofrequency emission from high to low spin state as is known in the art.NMR gives information on the type of environment of an atom, theneighboring environment based on the splitting pattern, the number ofprotons in environment (integral), and the symmetry of the molecule.Given a symmetrical molecule, corresponding proton and carbonenvironments are expected to be the same. In a symmetricalpyromellitamide the NMR data was thus expected to show 1 peak for theamide protons and 1 peak for the aromatic protons.

Referring to FIGS. 44-51 and Table 11, proton and carbon NMR data isillustrated for TH and TO.

TABLE 11 NMR peak data Gelling NMR FIG. agent Type Peak assignment 44 TH¹H N,N′,N″,N′″-tetrahexylbenzene-1,2,4,5-tetracarboxamide δ_(H) (300MHz, d₅-pyridine, Me₄Si) 0.75-0.85 (12H, m, CH₃), 1.15-1.27 (16H, m,CH₂), 1.30-1.42 (8H, m, CH₂), 1.69-1.77 (m, 8H, CH₂), 3.56-3.71 (8H, m,CH₂), 8.37 (1H, s, CH), 8.69 (1H, s, CH), 9.20 (1H, m, NH) and 9.29 (3H,m, NH). 45 TH ¹³C N,N′,N″,N′″-tetrahexylbenzene-1,2,4,5-tetracarboxamideδ_(C) (75 MHz, d₅- pyridine, Me₄Si) 14.2 (CH₃), 22.9 (CH₂), 27.1 (CH₂),29.9 (CH₂), 31.8 (CH₂), 40.5 (CH₂), 168.3 (C═O). 46/49 TO ¹HN,N′,N″,N′″-tetraoctylbenzene-1,2,4,5-tetracarboxamide δ_(H) (300 MHz,d₅- pyridine, Me₄Si) 0.81-0.89 (12H, m, CH₃), 1.10-1.30 (32H, m, CH₂),1.36-1.47 (8H, m, (CH₂), 1.74 (8H, tt, CH₂, J = 7.5 Hz), 3.59-3.76 (8H,m, CH₂), 8.35 (1H, s, CH), 8.68 (1H, s, CH), 9.15 (1H, t, NH, J = 5.7Hz) and 9.319 (3H, m, NH). 47/48 TO ¹³CN,N′,N″,N′″-tetraoctylbenzene-1,2,4,5-tetracarboxamide δ_(C) (75 MHz,d₅- pyridine, Me₄Si) 14.3 (CH₃), 22.9 (CH₂), 27.4 (CH₂), 29.5 (CH₂),29.6 (CH₂), 30.0 (CH₂), 32.0 (CH₂), 40.5 (CH₂), (2 aromatic peaksobscured by pyridine solvent peaks), 130.6 (C), 133.0 (C), 135.8 (C)160.4 (C═O) and 168.4 (C═O).

The NMR data appeared to indicate that the pyromellitamides analyzedwere unsymmetrical. For example, the ¹H NMR appears to indicate anunsymmetrical molecule by illustrating that the protons on the benzenering are in different environments. Referring to The ¹H data appears toshow 1 amide proton in a distinctly unique environment as evidenced by atriplet, whereas the 3 other amide protons are in similar environmentsas evidenced by overlaid triplets. FIG. 43, examples of possiblerotamers are shown that may cause this type of pattern. The molecules inFIG. 43 illustrate from left to right the (syn-syn)-(anti-anti),(syn-syn)-(syn-anti), and the (syn-syn)-(anti-anti) examples.

FIGS. 50-51 illustrate variable temperature (VT) ¹H NMR Spectra. The VT¹H NMR spectra provide evidence for H bonding, as well as evidence ofthe rotamer interconversion seen as the shape of the amide H peakschanged with increasing temperature indicating a changing environment,thus consistent with the data illustrated in FIG. 16. Referring to FIG.50, the ¹H NMR VT illustrated a stepwise decrease in chemical shift asthe temperature increased. A reduction in the extent of H-bonding astemperature is increased was also shown, which is consistent with thedata illustrated in FIG. 16. Referring to FIG. 51, the TO ¹H NMR VTillustrated an upfield shift, which is conventionally described asnegative temperature coefficient. In a hydrogen-bonded amide group, thecarbonyl functionality causes the amide proton to be shifted downfield.Increased temperature=increased magnitude of thermalfluctuations=increase in the average distance between atoms. Thus, thehydrogen bond is weakened and the amide proton is shifted downfield to alesser extent (i.e. a relative upfield shift).

Referring to FIGS. 52-53, both TH and TO show similar amide hydrogenshift temperature dependence.

The disclosed embodiments may provide low viscosity gels or highviscosity gels. An example of a low viscosity gel (2-50 cp) is SLICKOIL™ designed application is for tight oil and gas formations. Highviscosity gels may require addition of a breaker.

The base components of TG740, SF800 and SF 840 are alkanes, isoalkanesand aromatic hydrocarbons. TG740, SF800 and SF 840 are frac fluidsavailable for sale under the same or different names at variousrefineries in North America. SD810, or SynDril 810, is a drilling fluidavailable for sale under the same or different names at variousrefineries in North America.

The downhole fluids disclosed herein may be used as downhole treatmentfluids, as drilling fluids, or for other downhole uses. FIG. 63illustrates the fluid 30 being used as a drilling fluid in associationwith a drill bit 32 drilling a well 34. For a drilling fluid example, asample of Syndril 810 (SD810), which is a mineral oil, was mixed with 5mM TO. The mixture was mixed for 5 hours in a mixer at level 1-40% andleft mixing overnight. The sample wasn't fully dissolved by the morningso the sample was heated for 30 min at 70° C. before being mixed againfor 1 hour after which the TO had fully dissolved into the samplemixture. Viscosity was tested on a Fann Model 35A 6 speed Viscometeravailable from the FANN INSTRUMENT COMPANY™, of Houston, Tex. Viscosityresults are shown below in Table 12, and indicated a plastic viscosityof 10 cP and a yield point of 12 lbs/100 ft². The drilling fluid testingindicated that the resulting mixture has suitable viscosity and low endrheology (solids removal). The viscosity test was then repeated after awetting agent (described further above) was added (5 mL/L) to thesample. The viscosity results for the subsequent test with the wettingagent sample are shown below in Table 13, and indicate a plasticviscosity of 10 cP and a yield point of 11.5 lbs/100 ft². Drillingchemicals are generally large amines that don't affect the hydrogenbonding of the amide branched aromatic and pyromellitamide gel. Drillingfluids include inverts.

TABLE 12 Drilling fluid test results Speed (RPM) Viscosity (cP) 600/30044/34 200/100 30/26 6/3 21/19

TABLE 13 Drilling Fluid test results with Wetting Agent Speed (RPM)Viscosity (cP) 600/300 43/33 200/100 29/24 6/3 20/18

Table 14 illustrates further tests done with drilling fluid (5 mM TO inSD810, with rev dust and a wetting agent Dynol™ 604), and indicate aplastic viscosity of 17 cP and a yield point of 10.5 lbs/100 ft².

TABLE 14 Drilling fluid results with wetting agent Speed (RPM) Viscosity(cP) 3 18 6 19 100 26 200 32 300 38 600 55

Table 15 illustrates viscosity testing that compares a 5 mM TO gel inSD810 with various other drilling fluids. Table 16 indicates thecomponents present in the drilling muds tested. Viscosity and ESmeasurement taken at 25° C., and fluid loss was performed at 100° C. and500 psi differential pressure. As can be see, the SD810 drilling fluidshowed higher viscosity than comparable drilling muds.

TABLE 15 Further drilling fluid evaluation of DF-48 Drillsol Synoil Plus90/10 470 90/10 SynDril 810 BHR AHR BHR AHR Viscosity 600 rpm 65 46 4029 25 300 rpm 45 28 24 17 15 200 rpm 37 21 18 12 11 100 rpm 30 14 12 7 7 6 rpm 22 5 4 2 2  3 rpm 22 4 3 1 1 Plastic viscosity (mPa-s) 20 18 1612 10 Yield point (Pa) 12.5 5 4 2.5 2.5 ES - Electrical Stability <19991562 >2000 644 1777 (ave) HTHP - high temperature 4.6 5.3 6.1 highpressure (mL)

TABLE 16 Components of drilling fluids from Table 15 Drillsol Synoil 470Plus 90/10 90/10 Base fluid SynDril 810 BHR AHR BHR AHR DF-48 (TO) 3.30kg/m³ Wetting agent 4 L/m³ (Drilltreat from Halliburton) Rev Dust 50Kg/m³ 100 Kg/m³ 100 Kg/m³ Drillsol Plus 90/10 OWR Syndril 470 90/10 OWRBentone 150 20 Kg/m³ 20 Kg/m³ 30% CaCl₂ 90/10 OWR 90/10 OWR brineClearwater P 10 L/m³ 10 L/m³ Clearwater S 5 L/m³ 5 L/m³ Lime 12 Kg/m³ 12Kg/m³

Various N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) variants were tested andgelled in SynDril 810 at 5 mM, results shown in Table 17.

TABLE 17 viscosities of tetraamides in SynDril 810 (SD810) Gel nameViscosity (cP) N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) heptanamide 96-98N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) octanamide 87-89N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) nonanamide 85-87N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) decanamide 78-79N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) dodecanamide 16-18N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) tetradecanamide  8-10N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) hexadecanamide 71-73

Table 18 below illustrates viscosity test results for a drilling fluid(SD810) gelled with TO, and with a gel enhancer added, namelyhexamethylene diaminochloride (hexamethylene diamine dihydrogenchloride). The gel was made with a concentration of 1.2 mM (2.4 kg/m3)and had added to it a 9.6 mM enhancer (which is the equivalent of 80 mMwith 10 mM gel). The results indicate good low end rheology, for exampleat the 6/3 setting. Such results indicate that the fluid has cleaningpower at low flow rate, because the gel maintains sufficient viscosity.

TABLE 18 Viscosity of enhanced drilling fluid Gel after 5 mins InitialInitial gel after 1 hr blending with gel rest Intensifier RPM cP cP cP600/300 28/21 32/24 34/25 200/100 18/14 20/16 22/18 6/3 5/4 7/6 9/7

The base fluid may comprises fluid other than hydrocarbons. For example,the base fluid may include one or more of nitrogen or carbon dioxide.For further example N2 may be present at 50-95% while CO2 may be presentat 5-50%. Other ranges and other base fluids may be used. Hydrocarbonbase fluids may be combined with other fluids such as N2 and CO2 in somecases.

Gel Enhancers (Intensifiers)

The discovery of compounds that increase rather than decrease theviscosity of the pyromellitamide gelling agents led to the conclusionthat the pyromellitamide and amide branched aromatic gels may be used inconjunction with such gel enhancers. Co-use of gelling agent andenhancer may be synergistic and reduce the amount of gel required toachieve relatively comparable viscosities.

Suitable gel enhancers may be used. For example, the gel enhancer maycomprise one or more of a metal compound, potassium tert-butoxide,diethanolamine, L-menthol, lactic acid, mandelic acid, ammonium acetate,paraformaldehyde, hydroquinone, and tetramethylammonium hydroxide.

Potassium tert-butoxide and piperazine were tested as gel enhancers. Onetest performed was intended to determine if the enhanced gels could bebroken. Solutions were made up containing the already gelled TH in TG740hydrocarbon solution and a small amount of either potassiumtert-butoxide or piperazine. Five breaking agents, namely benzyltributylammonium chloride, 2-ethyl-1-butanol, 2-ethyl-1-hexylamine, benzylamine,and 1-butanol were tested against these solutions. These breakers hadworked well to destroy the hydrogen bond network in the standard gelledhydrocarbon solutions and were now used to determine effectiveness inthese thickened solutions. In non-enhanced solution these breakersimmediately returned the viscosity back to the original hydrocarbonviscosity. With potassium tert-butoxide present, benzyltributyl ammoniumchloride, 2-ethyl-1-butanol, and 1-butanol reduced viscosity immediatelyupon mixing. However, 2-ethyl-1-hexylamine decreased viscosity onlyslightly, and benzylamine didn't reduce viscosity noticeably. Forpiperazine, benzyltributyl ammonium chloride, 2-ethyl-1-butanol,benzylamine, and 1-butanol all reduced viscosity noticeably aftermixing, while 2-ethyl-1-hexylamine decreased viscosity only slightly.None of these breakers worked as well in enhanced solutions as in nonenhanced solutions. 2-Ethylhexanol could also be used as a breaker.

After noticing that piperazine thickens the solution and increased theviscosity of the already gelled solution, several tests were done to seeif the amount of pyromellitamide gelling agent could be reduced usingpiperazine whilst still giving the same relative viscosity level. Thestandard gel solution that the viscosity of the various compositionswere measured and compared against was an 8.0 mmol solution of the THsolution (24 mg in 5 mL of TG 740 hydrocarbon). First tested was a 10%gel solution with 0.8 mmol tetramide (2.4 mg/5 mL) and 7.2 mmolpiperazine (3.1 mg/5 mL). This ratio didn't seem to increase theviscosity of the solution in comparison to the starting hydrocarbon gelsolution, even when excess of piperazine was added (up to 12 times morepiperazine compared to tetramide) suggesting that a certain baseconcentration, for example at least the 50% solution tested next, of thetetramide must be present in order for the enhancement to besignificant. Next a 50% gel solution was tested: 4.0 mmol tetramide (12mg/5 mL) and 4.0 mmol piperazine (1.7 mg/5 mL). The solution becamethicker than the original hydrocarbon but not quite as thick as thestandard 8 mmol tetramide gelled solution. Next a 1:2 ratio gel solutionwas tested: 4.0 mmol tetramide (12 mg/5 mL) and 8.0 mmol piperazine (3.4mg/5 mL). Having double the amount of piperazine increased the viscosityof the solution in comparison to the previous test, making the solutionabout as thick as the standard 8.0 mmol tetramide solution. Next a 1:3ratio gel solution: 4.0 mmol tetramide (12 mg/5 mL) and 12.0 mmolpiperazine (5.1 mg/5 mL). This gel seemed to have a slight effect onincreasing the viscosity however the solution wasn't as thick as in the1:2 ratio gel, possibly indicating that piperazine can also act as abreaker, thickening the solution when a small amount is added, but thenbreaking it when an excess is used. Next a 60% gel solution was tested:4.8 mmol tetramide (14.4 mg/5 mL) and 3.2 mmol piperazine (1.38 mg/5mL). This combination increased the viscosity of the solutionnoticeably, and became as thick if not slightly thicker than thestandard 8 mmol tetramide solution normally used. Finally, an 80% gelsolution was tested: 6.4 mmol tetramide (19.2 mg/5 mL) and 1.6 mmolpiperazine (0.68 mg/5 mL). This combination increased the viscosity morethan the standard 8 mmol tetramide solution. The gel enhancer may bepresent at or above a ratio of enhancer:gel of 1:1, or 50%, in somecases.

Several other molecules were tested to see if they thickened (enhanced)the regular TH gel solution. Three chemicals that achieved this resultwere L-menthol, paraformaldehyde and hydroquinone. Thus the compositionof the original gel solution 8 mmol (24 mg in 5 ml hydrocarbon) wasaltered to see if less of the tetramide could be used, withoutdiminishing the viscosity of the gelled solution. Each chemical wastested in three different compositions: 1) 50:50 solution: 4.0 mmoltetramide, 4.0 mmol other chemical all in 5 ml of hydrocarbon, 2) 60:40solution: 4.8 mmol tetramide, 3.2 mmol other chemical all in 5 ml ofhydrocarbon, and 3) 80:20 solution: 6.4 mmol tetramide, 1.6 mmol otherchemical all in 5 ml of hydrocarbon. For L-menthol, the firstcomposition had almost no effect on viscosity, the second caused aslight increase in viscosity, and the third composition was almost asviscous as the standard 8 mmol tetramide solution. Paraformaldehydeperformed comparably with L-menthol. For hydroquinone, the firstcomposition had almost no effect on viscosity, the second increasedviscosity more than the other two compounds despite still not achievingthe same viscosity as the standard 8 mmol solution, and the thirdcomposition was as viscous as the standard 8 mmol solution and thickerthan the viscosity caused by the other two compounds.

Although hydroquinone appeared to be the most effective thickening agentof these three tested, with an 80:20 gel:enhancer ratio showingviscosity comparable to a 100:0 ratio, none of these three chemicalsworked as well as piperazine in this regard. However, the resultsindicate that hetrocycles, for example with a 1,4 relationship, may workas gel enhancers given that piperazine and hydroquinone seemed toincrease viscosity the most of all compounds tested. Thus, the gelenhancer may comprise cyclic heterocycles in some embodiments, forexample heterocycle with at least two heteroatoms (neither carbon norhydrogen) spaced from one another and each having one or more lone pairsof electrons. As stated one 6 atom ring heterocycle example ispiperazine. In other embodiments the heterocycle may form a 6 atom ringwith the two non carbon atoms located at the 1 and 4 positions or onrespective functional groups originating from the 1 and 4 positions.Nitrogen donors may work better than oxygen donors, most likely becauseof nitrogen's lower electronegativity, which allows its lone pairs todonate better and form more hydrogen bonds. Heterocycles or other typesof cross-linkers are believed to work in a fashion similar to clayplatelets in drilling, in that the compounds can hydrogen bond on bothsides of the compound, thus linking two adjacent gel chains together.

As demonstrated elsewhere in this application, tetramethylammoniumhydroxide was tested along with tetra-n-butylammonium hydroxide asadditives to the tetramide gel solution to see if breaking or enhancingwould occur. The tetra-n-butylammonium hydroxide broke the gel solutiononce added, however tetramethyl ammonium hydroxide thickened up thesolution, thus, showing two different results, which may be due to thedifferent chain lengths of the alkyl groups attached to the nitrogenatom. Like with piperazine, the effect of tetramethyl ammonium hydroxidewas tested by replacing a portion of the gel with tetramethyl ammoniumhydroxide to see if viscosity could be maintained while using lesstetramide gel. As before, the benchmark for viscosity was the 8 mmolsolution (24 mg tetramide in 5 ml of TG 740 hydrocarbon). The firstcomposition tested was a 50:50 solution: 4.0 mmol tetramide, 4.0 mmoltetramethyl ammonium hydroxide all in 5 ml of hydrocarbon. Thiscomposition caused a slight increase in viscosity at a level comparablewith the other gel enhancers. The next composition tested was a 60:40solution: 4.8 mmol tetramide, 3.2 mmol other chemical all in 5 ml ofhydrocarbon. This composition showed a similar result as the 50:50composition. The last composition tested was a 80:20 solution: 6.4 mmoltetramide, 1.6 mmol other chemical all in 5 ml of hydrocarbon. Againthis composition caused no great change in viscosity although thesolution remained thick but not as thick as the standard 8 mmoltetramide gel solution. Overall, the tetramethylammonium hydroxide wasless effective than piperazine but did show that some of the tetramidecould be replaced by another chemical without the viscosity beingreduced.

The metal compound gel enhancer, such as a metal salt, may comprise acation, such as one or more of iron and aluminium. The cation may becomplexed, for example chelated using one or more surfactants, toimprove solubility in the base fluid. For example, referring to FIGS.58-60 iron activator in the form of iron (III) sulfate, provided byHGA-65 sold by Weatherford International, was tested in differentamounts in the DF-46 gel. HGA-65 is an organo-metallic complextraditionally used as an activator for phosphate ester gelling agents inhydrocarbon frac fluids. HGA-65 contains citric acid, and amines. FIG.58 illustrates addition of the gel enhancer after gel formation, anddemonstrates that more enhancer equals greater viscosity. FIG. 59illustrates that addition of the gel enhancer may speed up gelling. FIG.60 illustrates that the positive effects may drop off as theconcentration of pyromellitamide gelling agent decreases past apredetermined concentration or range of concentrations. Success withcomplexed iron sulfate was unexpected given that pure iron sulfate wasshown to have a breaking effect on the gel. However, it is believed thatthe complexing agents provided with the iron sulfate pull the ironcation into solution within the hydrocarbon base fluid, and bring theiron near the gelling agent molecules where cross-linking with gelmolecules may occur or the iron may improve hydrogen bond stabilitybetween gel molecules. The breaking action of the pure iron sulfate isthought to be due to the polar iron sulfate chaotropically drawing thegelling agent out of solution with the base fluid.

Other metal compounds, such as polyvalent metal salts, including zinc,may be used. It is thought that the gel enhancer works by cross-linkingadjacent gel molecules or by facilitating cross-hydrogen bonding betweenadjacent gel molecules. The gel enhancer may be present with asurfactant for dispersing the gel enhancer in the base fluid, forexample in the case of iron sulfate where citrate and amines arepresent. Dispersing such as dissolving into solution allows the gelenhancer to access the gel molecules in order to carry out the desiredenhancement. In other cases the gel enhancer may be soluble in pure formin the base fluid.

In general, compounds like metal salts that are able to cross link thegel to provide additional viscosity may be used as gel enhancers. Forexample, Al3+ and Fe3+ have been tested and both work. At higherconcentrations, complexed iron (III) sulphate may be less effective asan enhancer. Al3+ may be provided in the form of aluminum isopropoxide,with the Al part enhancing gelling and the propoxide breaking the gel asdiscussed above, so that the viscosity profile contains a spike inviscosity. Other metal alkoxides may be used as gel enhancers, and insome cases as breakers as well, for example as a water activatablebreaker provided in conjunction with a hydrate in the fluid to releasewater and transform alkoxide into alcohol. In some cases alkoxides areexcluded as gel enhancers.

As disclosed above, the gelling agent may form a hydrogen-bond networkthrough intermolecular hydrogen bonds between the amide branches ofadjacent gelling agent molecules. The gel enhancer may improve gellingby cross-linking the intermolecular hydrogen bonds or facilitating theintermolecular hydrogen bonds. Cross-linking may be done by hydrogenbond bridging two amide branches with an enhancer. Facilitation mayinclude stabilization a direct hydrogen bond between amide branches.

The gel enhancer may comprise a salt of an aromatic carboxylic acid,such as an ibuprofen salt (Table 0). Other salts include salts ofhydrocinnamic acid, diphenylacetic acid, benzoic acid, and phenylaceticacid. It is believed that the COO— hydrogen bonds between amide branches(cross-linking), and the aromatic moiety on the enhancer interacts withthe aromatic moiety on the gel, stabilizing the gel. As discussed abovethe COO— salt may be more water soluble than the COOH and thus the saltmay only be retained at a relatively low concentration in thehydrocarbon phase with the gel. By contrast the protonated COOH versionsof aromatic carboxylic acids may act as breakers of the gel, see above.

As discussed above, the gel enhancer may also operate as a breaker indifferent conditions or configurations. One example of a dual functionbreaker/enhancer is an aromatic carboxylic acid. A modifier may be addedto the gel, the modifier being selected to convert the gel enhancer intoa breaker. In some cases, the gel enhancer is present in the gel below athreshold concentration above which the gel enhancer becomes a breaker,and in which the modifier comprises an additional source of gel enhancersufficient to raise the concentration of gel enhancer to above thethreshold concentration. Examples of concentration dependent dualfunction breaker/enhancers include piperidine (see Table 0) andpiperazine. The additional source of enhancer may be supplied in acoated form for delayed release. In other cases, the modifier may be achemical selected to chemically modify the existing gel enhancer. Forexample, if piperidine is used as an enhancer, the modifier may comprisebenzylamine. For further example, if an aromatic carboxylic acid salt isused as an enhancer, the modifier may comprise a protonation source suchas an acid, or a cation complexing agent such as citric acid.

The gel enhancer may comprise one or more of ammonium chloride,melamine, choline chloride, and hexamethylene diaminochloride (Table 0).Other enhancers may be used.

In some cases one or more, for example each, of the amide branches areconnected to the aromatic core via a carbon-nitrogen bond. Structures(8)-(12) are examples of such gelling agents. The gelling agents mayhave three or four amide branches, for example four as shown below. Eachorganic group may be an alkyl group, such as a C6-24 straight chainalkyl group as shown below. FIG. 64 illustrates the viscosityperformance of compounds (8), (9), and (12), at 5 mM in TG740 at roomtemperature.

Preparation of N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl)tetrahexanamide (8)

Procedure. Benzene-1,2,4,5-tetraammonium chloride (2.0 g, 7.0 mmol),triethylamine (5.8 cm3, 42.0 mmol) and dry tetrahydrofuran (150 cm3)were added to a round bottom flask charged with a magnetic stirrer andmixed thoroughly until most of the solid had dissolved. To the solutionhexanoyl chloride (4.9 cm3, 35.0 mmol) was added slowly, causing thepink colour in the solution to disappear and a white precipitate toform. The solution was filtered, the solvent removed using a rotaryevaporator and the crude orange solid dissolved in toluene (50 cm3) andadded dropwise to a solution of vigorously stirred ethanol (200 cm3) tore-precipitate the product. The white solid was filtered off and driedunder vacuum to give the desired product as a slightly sticky off-whitesolid (2.43 g, 61.8%).

Preparation of N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) tetraheptanamide(9)

Procedure. Benzene-1,2,4,5-tetraammonium chloride (1.0 g, 3.5 mmol),triethylamine (2.8 cm3, 20.0 mmol) and dry tetrahydrofuran (50 cm3) wereadded to a round bottom flask charged with a magnetic stirrer and mixedthoroughly until most of the solid had dissolved. To the solutionheptanoyl chloride (2.3 cm3, 15.0 mmol) was added slowly, causing thedark pink solution to turn brown and a precipitate to form. The solutionwas filtered, the solvent removed using a rotary evaporator yielding anorange solid that when dissolved in toluene (30 cm3) and added to asolution of vigorously stirred ethanol (200 cm3) to re-precipitate theproduct. The white solid was filtered off and dried under vacuum to givethe desired product as a slightly sticky off white solid (0.88 g,43.0%).

Preparation of N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) tetraoctanamide(10)

Procedure. Benzene-1,2,4,5-tetraammonium chloride (1.0 g, 3.5 mmol),triethylamine (2.8 cm3, 20.0 mmol) and dry tetrahydrofuran (50 cm3) wereadded to a round bottom flask charged with a magnetic stirrer and mixedthoroughly until most of the solid had dissolved. To the solutionoctanoyl chloride (2.5 cm3, 15.0 mmol) was added slowly, causing thedark pink solution to turn brown and a precipitate to form. The solutionwas filtered, the solvent removed using a rotary evaporator yielding anorange solid that when dissolved in toluene (30 cm3) and added to asolution of vigorously stirred ethanol (200 cm3) to re-precipitate theproduct. The white solid was filtered off and dried under vacuum to givethe desired product as an off white solid (1.17 g, 51.7%).

Preparation of N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) tetradecanamide(11)

Procedure. Benzene-1,2,4,5-tetraammonium chloride (1.0 g, 3.5 mmol),triethylamine (2.8 cm3, 20.0 mmol) and dry tetrahydrofuran (50 cm3) wereadded to a round bottom flask charged with a magnetic stirrer and mixedthoroughly until most of the solid had dissolved. To the solutiondecanoyl chloride (3.1 cm3, 15.0 mmol) was added slowly, causing thedark pink solution to turn brown and a precipitate to form. The solutionwas filtered, the solvent removed using a rotary evaporator yielding anorange solid that when dissolved in toluene (30 cm3) and added to asolution of vigorously stirred ethanol (200 cm3) to re-precipitate theproduct. The white solid was filtered off and dried under vacuum to givethe desired product as an off white solid (1.24 g, 46.6%).

Preparation of N,N′,N″,N′″-(benzene-1,2,4,5-tetrayl) tetradodecanamide(12)

Procedure. Benzene-1,2,4,5-tetraammonium chloride (1.0 g, 3.5 mmol),triethylamine (2.8 cm3, 20.0 mmol) and dry tetrahydrofuran (50 cm3) wereadded to a round bottom flask charged with a magnetic stirrer and mixedthoroughly until most of the solid had dissolved. To the solutiondodecanoyl chloride (3.6 cm3, 15.0 mmol) was added slowly, causing thedark pink solution to turn brown and a precipitate to form. The solutionwas filtered, the solvent removed using a rotary evaporator yielding anorange solid that when dissolved in toluene (30 cm3) and added to asolution of vigorously stirred ethanol (200 cm3) to re-precipitate theproduct. The white solid was filtered off and dried under vacuum to givethe desired product as an off white solid (1.34 g, 44.0%).

TABLE 19 Percentage yield, melting point, and viscosity values of theN,N′,N″,N′″-(benzene-*) gels Average Average Abbreviated Yield m.p.Viscosity in Viscosity in compound name (%) (° C.) TG740 (cP) SynDrill810 (cP) Hexanamide 61.8 Decomposed 40.93 Insoluble Heptanamide 40.3Decomposed 65.49 96.41 Octanamide 51.7 Decomposed Insoluble 88.16Nonanamide 41.2 Decomposed 11.39 84.64 Decanamide 46.6 299.8-300.4 24.6678.34 Dodecanamide 44.0 300.1-301.6  0.56 15.47

In some embodiments the gelling agent has the form of compounds (13) or(14) below, in which R independently represent hydrocarbon or ahydrocarbon group with 1-29 carbon atoms, and R1 independentlyrepresents a hydrocarbon group with 1-29 carbon atoms. Further examplesof these and other suitable gelling agents are disclosed in U.S. Pat.No. 6,645,577, which describe gel forming compounds. Such compounds arebelieved to be thus suitable for use with downhole fluids. A synthesisexample of one such compound (15) is detailed below.

Procedure. In 70 ml of tetrahydrofuran (THF), 0.7 g of1,3,5-benzenetricarboxylic acid and 2.5 g of stearylamine weredissolved. To the solution, 3.6 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (WSC: water-soluble carbodiimide) and 2.52 gof 1-hydroxy-1H-benzotriazole (HOBT) were added, and then 5 ml oftriethylamine (TEA) was added dropwise on an ice bath. After theaddition, the mixture was stirred for 2 hours on the ice bath andfurther stirred at room temperature. The reaction mixture was recoveredby filtration and dissolved in chloroform. Successive washings withdiluted hydrochloric acid, sodium bicarbonate aqueous solution, andwater followed. The product was dried with anhydrous sodium sulfate andrecrystallized to obtain 4.0 g of an objective compound (15) shownabove.

In some embodiments one or more of the amide branches is connected tothe aromatic core via a carbon-carbon bond and one or more of the amidebranches are connected to the aromatic core via a carbon-nitrogen bond.Examples of such structures with varying proportions of N—C and C—Cconnections include the form of compounds (16)-(18) below:

In the examples of (16)-(18) above, R1, R2 and R3, or Y1, Y2 and Y3, orZ1, Z2 and Z3 independently of one another are C1-C20alkyl unsubstitutedor substituted by one or more hydroxy; C2-C20alkenyl unsubstituted orsubstituted by one or more hydroxy; C2-C20alkyl interrupted by oxygen orsulfur; C3-C12cycloalkyl unsubstituted or substituted by one or moreC1-C20alkyl; (C3-C12cycloalkyl)-C1-C10alkyl unsubstituted or substitutedby one or more C1-C20alkyl; bis[C3-C12cycloalkyl]-C1-C10alkylunsubstituted or substituted by one or more C1-C20alkyl; a bicyclic ortricyclic hydrocarbon radical with 5 to 20 carbon atoms unsubstituted orsubstituted by one or more C1-C20alkyl; phenyl unsubstituted orsubstituted by one or more radicals selected from C1-C20alkyl,C1-C20alkoxy, C1-C20alkylamino, di(C1-C20alkyl)amino, hydroxy and nitro;phenyl-C1-C20alkyl unsubstituted or substituted by one or more radicalsselected from C1-C20alkyl, C3-C12cycloalkyl, phenyl, C1-C20alkoxy andhydroxy; phenylethenyl unsubstituted or substituted by one or moreC1-C20alkyl; biphenyl-(C1-C10alkyl) unsubstituted or substituted by oneor more C1-C20alkyl; naphthyl unsubstituted or substituted by one ormore C1-C20alkyl; naphthyl-C1-C20alkyl unsubstituted or substituted byone or more C1-C20alkyl; naphthoxymethyl unsubstituted or substituted byone or more C1-C2alkyl; biphenylenyl, flourenyl, anthryl; a 5- to6-membered heterocylic radical unsubstituted or substituted by one ormore C1-C20alkyl; a C1-C20 hydrocarbon radical containing one or morehalogen; or tri(C1-C10alkyl)silyl(C1-C10alkyl); with the proviso that atleast one of the radicals R1, R2 and R3, or Y1, Y2 and Y3, or Z1, Z2 andZ3 is branched C3-C20alkyl unsubstituted or substituted by one or morehydroxy; C2-C20alkyl interrupted by oxygen or sulfur; C3-C12cycloalkylunsubstituted or substituted by one or more C1-C20alkyl;(C3-C12cycloalkyl)-C1-C10alkyl unsubstituted or substituted by one ormore C1-C20alkyl; a bicyclic or tricyclic hydrocarbon radical with 5 to20 carbon atoms unsubstituted or substituted by one or more C1-C20alkyl;phenyl unsubstituted or substituted by one or more radicals selectedfrom C1-C20alkyl, C1-C20alkoxy, C1-C20alkylamino, di(C1-C20alkyl)amino,hydroxy and nitro; phenyl-C1-C20alkyl unsubstituted or substituted byone or more radicals selected from C1-C20alkyl, C3-C12cycloalkyl,phenyl, C1-C20alkoxy and hydroxy; biphenyl-(C1-C10alkyl) unsubstitutedor substituted by one or more C1-C20alkyl; naphthyl-C1-C20alkylunsubstituted or substituted by one or more C1-C20alkyl; ortri(C1-C10alkyl)silyl(C1-C10alkyl).

Further examples of (16)-(18) and other suitable gelling agents aredisclosed in U.S. Pat. No. 7,790,793, which describes gelling agents forthe preparation of gel sticks and that improve the gel stability ofwater and organic solvent based systems. Such gelling agents arebelieved to be thus suitable for use with downhole fluids. A synthesisexample of one such compound (19) is detailed below.

1.00 g (4.3 mmol) of 1,3,5-triaminobenzene trishydrochloride (SeeExample A) and 0.1 g of LiCl are added under inert atmosphere to 50 mlof dry NMP and 10 ml of dry pyridine and cooled to 5.degree. C. 1.73 g(14.3 mmol) of pivaloyl chloride is added. The reaction mixture isheated to 60.degree. C. and stirred. After 24 hours the reaction mixtureis added to 1000 ml of ice water. The precipitate is filtered off.Customary work-up (recrystallization from tetrahydrofuran) gives thedesired product (19).

As shown above, the gelling agents may have benzene as an aromatic core.However, other aromatic cores may be used. For example, naphthalene maybe used as an aromatic core. Aromatic cores may be flat and are expectedto facilitate the formation of the layered gel mechanism discussedabove.

As shown above, each amide branch may have one organic group or sidechain. However, in some cases one or more of the amide branches have twoorganic groups. For example, the amide branch connects to the aromaticcore via a carbon-nitrogen bond, the nitrogen has an alkyl group and thecarbonyl carbon has an organic group. Other examples may be used. One ormore amide branches may have two organic groups on the amide nitrogen,so long as at least one, two, or more amide branches have an amidenitrogen with a free hydrogen for hydrogen bonding. In other cases eachamide branch nitrogen has one hydrogen atom for maximum facilitation ofhydrogen-bonding and gel formation.

Non-alkyl organic side chains may be used. Organic groups with five orless carbon atoms may be used.

In the claims, the word “comprising” is used in its inclusive sense anddoes not exclude other elements being present. The indefinite article“a” before a claim feature does not exclude more than one of the featurebeing present. Each one of the individual features described here may beused in one or more embodiments and is not, by virtue only of beingdescribed here, to be construed as essential to all embodiments asdefined by the claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A fluid comprising abase fluid, a gelling agent, a gel enhancer and a modifier selected toconvert the gel enhancer into a breaker, in which the gelling agent hasan aromatic core of one or more aromatic rings, the gelling agent hastwo or more amide branches distributed about the aromatic core, and eachof the two or more amide branches has one or more organic groups, and inwhich the gelling agent forms a hydrogen-bond network throughintermolecular hydrogen bonds between the amide branches of adjacentgelling agent molecules, and in which the gel enhancer cross-links theintermolecular hydrogen bonds or facilitates the intermolecular hydrogenbonds.
 2. The fluid of claim 1 in which the gel enhancer is presentbelow a threshold concentration above which the gel enhancer becomes abreaker, and in which the modifier comprises an additional source of gelenhancer sufficient to raise the concentration of gel enhancer to abovethe threshold concentration.
 3. A fluid comprising a base fluid, agelling agent, and a gel enhancer, in which the gelling agent has anaromatic core of one or more aromatic rings, the gelling agent has fouramide branches distributed about the aromatic core, and each of theamide branches has one or more organic groups.
 4. A fluid comprising abase fluid, a gelling agent, and a gel enhancer, in which the gellingagent has an aromatic core of one or more aromatic rings, the gellingagent has two or more amide branches distributed about the aromaticcore, and each of the two or more amide branches has one or more organicgroups, in which the gelling agent is a pyromellitamide gelling agentand has the general formula of:

with R₁, R₂, R₃, R₄, R₅, R₆, R₇, and R₈ each being a hydrogen or anorganic group.
 5. The fluid of claim 4 in which R₅, R₆, R₇, and R₈ areeach hydrogens and one or more of R₁, R₂, R₃, and R₄ are each an alkylgroup.
 6. The fluid of claim 5 in which R₁, R₂, R₃, and R₄ are eachalkyl groups.
 7. The fluid of claim 6 in which R₁═R₂═R₃═R₄.
 8. The fluidof claim 7 in which R₁, R₂, R₃, and R₄ each have at least 6 carbonatoms.
 9. The fluid of claim 6 in which each alkyl group has 6-24 carbonatoms.
 10. The fluid of claim 9 in which each alkyl group has 6-10carbon atoms.
 11. The fluid of claim 5 in which each alkyl group is oneor more of straight chain, branched, or cyclic.
 12. The fluid of claim11 in which each alkyl group is straight chain.
 13. The fluid of claim12 in which R₅, R₆, R₇, and R₈ are each hydrogens, and R₁, R₂, R₃, andR₄ are each straight chain alkyl groups with 6-10 carbon atoms.
 14. Thefluid of claim 13 in which R₁, R₂, R₃, and R₄ have 6 carbon atoms. 15.The fluid of claim 9 in which each alkyl group has 6 carbon atoms.
 16. Afluid comprising a base fluid, a gelling agent, a gel enhancer, and abreaker, in which the gelling agent has an aromatic core of one or morearomatic rings, the gelling agent has two or more amide branchesdistributed about the aromatic core, and each of the two or more amidebranches has one or more organic groups, in which the breaker furthercomprises a coating.
 17. The fluid of claim 16 in which the coatingfurther comprises wax.
 18. The fluid of claim 9 in which each alkylgroup has 8 carbon atoms.
 19. A fluid comprising a base fluid, a gellingagent, and a gel enhancer, in which the gelling agent has an aromaticcore of one or more aromatic rings, the gelling agent has four or moreamide branches distributed about the aromatic core, and each of the fouror more amide branches has one or more organic groups, in which each ofthe amide branches is connected to the aromatic core via a carbon-carbonor carbon-nitrogen bond, and in which one or more of the amide branchesare connected to the aromatic core via a carbon-nitrogen bond.
 20. Afluid comprising a base fluid, a gelling agent, and a gel enhancer, inwhich the gelling agent has an aromatic core of one or more aromaticrings, the gelling agent has four amide branches distributed about thearomatic core, and each of the four amide branches has one or moreorganic groups, in which each of the amide branches is connected to thearomatic core via a carbon-carbon or carbon-nitrogen bond, and in whichone or more of the amide branches are connected to the aromatic core viaa carbon-nitrogen bond.
 21. A fluid comprising a base fluid, a gellingagent, a gel enhancer, and a breaker, in which the gelling agent has anaromatic core of one or more aromatic rings, the gelling agent has twoor more amide branches distributed about the aromatic core, and each ofthe two or more amide branches has one or more organic groups, whereinthe breaker comprises ibuprofen.
 22. The fluid of claim 18 in which eachalkyl group is a straight chain alkyl group.
 23. The fluid of claim 15in which each alkyl group is a straight chain alkyl group.